Gravitational radiation in ultrarelativistic collisions

P. Spirin1

Abstract

Classical ultrarelativistic gravitational bremsstrahlung in particle collisions is studied in the ADD model with d extra dimensions. The main goal in this consideration concerns trans-Planckian energies. The radiation efficiency ep ºErad/Einitial is computed in terms of the Schwarzschild radius rS(…collision), the impact parameter b and the center-of-mass Lorentz factor gcm and is found to be ep = Cd (rS/b)3d + 3 times gcm in some d-dependent power, larger than the previous estimates by powers of gcm >> 1. The cubic graviton vertex is consistently taken into account, and the approximation is reliable for impact parameters in the range rS < b < bc, with bc marking (for d¹ 0) the loss of the notion of classical trajectories. It follows that gravitational bremsstrahlung leads to extreme damping in trans-Planckian collisions, and the radiation reaction should be included in the analysis of black hole production.